It's intended to solve exactly this problem, but in reverse -- a tarball is extracted to source, and we want to ensure that the sources we've extraced can be traced back to the original tarball.
Hum, that is interesting. I'm more thinking that in a perfect world the pristine-tar delta file should be empty. (Assuming I understand what pristine-tar is doing correctly).
For example I tend to use SOURCE_DATE_EPOCH to be the timestamp of the commit to make sure that anything that embed time is reproducible without extra instruction/manual process specific file.
https://manpages.debian.org/stretch/pristine-tar/pristine-ta...
It's intended to solve exactly this problem, but in reverse -- a tarball is extracted to source, and we want to ensure that the sources we've extraced can be traced back to the original tarball.